Airplane



April 21, 1931.

E. M. TORKELSON 1,802,226

AIRPLANE 3 Sheets-Sheet -l Filed June 1, 1927 w. 1/ I I Z/ Ef/NQVDENQ'E 2 2' ZERO LIFT LINE Q M v 0 1 07453616021 Wr-rwsgstaa Q4, 4

v V a: v I r r v fl'ftmq April 21, 1931. TORKELSQN 1,802,226

AIRPLANE Filed June 1, 1927 s Sheets-Sheet 2 jwwnloe:

IlllllllllIIlIIlIIlII-!3 IIi i 6 A rii 21; 1931.

E. M. TORKELSQN AIRPLANE Filed June 1, 1927 S Sheets-Sheet 3 gnwntoc EM 1614842 16010 Patented Apr. 21, 1931 PATENT OFFICE EILET MARTINTORKELSON, OF'ELIZABE'IE, NEW JERSEY AIRPLANE Application filed June 1,

This invention relates to airplanes and more particularly to novel automatic stabilizin means therefor.

To that end the invention contemplates a simple and practical means which may be readily set to automatically control a main stabilizing airfoil during flight of theairplane, and which will prevent the plane going into a stall and also preserve longitudinal dihedral angle.

A further object of the invention is to provide automatic stabilizing means which damps the oscillation of the tail of the plane, and also adjusts the stability to varying loads, as for example in the case of a bomb carrying plane when the b mb is dropped.

j A further object of the invention is to 2 provide a device which comprises a pair 0 airfoils ivotally mounted about different axes an adapted to have a differential movement which produces the desired correction.

With the above which will more readily appear as them.- ture of theinvention is'better understood, the same consists in the novel construction, combination and arrangement of parts hereinafter more. fully described, illustrated and 5 claimed.

A preferred and practical embodiment of the invention is shown in the accompanying drawings in which Fig. 1 is a vertical sectional view of the tail of an airplane embodying the present improvements. v

Fig. 2 is a top plan view of the construction shown in Fig. 1.

Fig. 3 is a vertical sectional view taken on the line 3-3 of Fig. 1.

Fig. 4 is an enlarged detail sectional view illustrating the pivot axis of the main stabilizing airfoil and part of the controlling means for the auxiliary airfoil.

Fig. 5 is a diagram illustrating the theoretical operation of the main and auxiliary airfoils.

Fig. 6 is a diagram, illustrating the relalongitu- 10 dinal stability by automatically varying the i a horizonta rudder or stabilizer sub ect to f manipulating the same.

and other objects in view P an 1927. semi no. 195,794.

tive angular movement of the main and auxiliary airfoils. I

Fig. 7 is a diagram illustratirgfithe manner of determining the dowpwa angle.

Fig. 8 is a side elevation of an airplane g5 embodying the present improvements. Similar reference characters designate corresponding parts throughout the. several figures of the drawings. i j

Ordinaril the majority of airplanes have m the control of the pilot and adapted to be manually manipulated to vary thelongitudinal dihedral angle to preserve longitudinal stability.

However, it is the object of the present invention to render the stabilizing airfoil automatic in its operation thereby relieving the pilot of the necessity of continuously In other words during the course of flight the automatic means rovided will manipulate the main stabilizing airfoil without manual attention, and in proportion to the deflection of the from its normal course, once the initial angle of the auxiliary airfoil is set by the control stick. Accordingly, as will be observed from the drawings, t e present invention includes in its organization a main stabilizing airfoilgo- A arranged at the tail of the fuselage of the airplane, and an auxihary controlling airfoil B mounted on a' bracket or lever arm G carried by the main airfoil and extending forwardl toward the wing posiac tions of the airp ane. The said arm C is arranged at the central part of the main airfoil A between the vertical fins D which are alined with the vertical rudders E.

The main stabilizing airfoil'A is prefer- 9o ably pivotally supported on the fuselage of the plane by a pivot axle l or its equivalent mounted in the journals 2 thereby to permit the airfoil to have a rockin movement in the usual manner to correct t e longitudinal 9 5 line of flight of the machine. As previously indicated, the bracket arm C is rigidly connected to the medial portion of the main stabilizing airfoil A and extends upwardly and forwardly at a suitable angle and pivotall receives or carries the controlling airfoil The said airfoilB is mounted on a rockable pivot 3 in the arm C and is provided ad acent the arm with a pulle 4 which receives a belt, chain or its uiva ent 5 that leads to the relatively smal pulley portion 6 of the main control pulley G loosey mounted on the pivot shaft 1. The pulley rtion 7 of larger diameter receives an a iilsting cable, rope chain or equivalent 8 which is looped thereabout and passes over the direction controlling pulleys 9-9 mounted on the bottom of the fuselage and has its ends connected to the terminals 10 and 11 of the control lever 12. a

In the normal use of the present stabilizdevice which includes the main stabiliz- "located in front thereof A and the auxiliary airfoil B and in the path of the downwash from the-main wings of the ages, the said auxiliary airfoil B, having n set tothe desired position by the pilot, tends to always assume a position which is governed by the downwash of the front wings re ardless of the movement of the plane. us, the auxiliary plane moves or operates the main stabilizing airfoil up or down to shift the plane into its normal position. The main airfoil A and auxiliary airfoil B are connected by an arm which is into al with the airfoil A, moving with it, whi e the airfoil B is connected to the arm through a pivot. It is therefore apparent that merely the angular rotation of the air foil B about its pivot is the only operation controlled by the stick in the cock pit. Al-

mg airfo though the airfoil B is smaller than the 7 'main airfoil A, the airfoil B will control the mentarily happen airfoil A through an angular motion about its pivot, due to the tremendous levera e exerted by means of connecting arm, the arger airfoil A also being'more or less balanced on its ivot at the return of theship structure. he airfoil B always has the tendency to remain in a position which will have its angle neutral to the downwash angle from the front main wings whatever that may moto be. It is therefore apparent that should the downwash vary, either through a chan e in air currents, or in the lightening of t 0 load of the ship, this momentary change of the downwash angle will tend to move the auxiliary plane B through a distance according to its initial angular setting and so control the rear airfoil A by exerting a torque against it of the relatively long connecting arm.

If the pilot intends to follow a horizontal course after gaining his altitude he manipulates the control lever 12 to set the auxiliary controlling airfoil B in the proper position to keep the plane on a horizontal course. In that connection the horizontal axis of the airfoil B ma or ma not be parallel with the axis of e airfoil A. In the arrangeleys 4 and 6. Accor ment shown in the drawings there will always be a sli ht download on the auxiliary airfoil B to alance the horizontal component of force on the airfoil A. If the plane strikes bumpy air or attempts to go into a stall, the auxiliary airfoil B will be moved by the increased pressure due to additional resistance encountered and proportionately move the main stabilizing airfoil thereby to firing the plane back into the path of normal i ht.

aving described the general structural features and characteristics of the invention, reference will now be made to the theory and application of the invention from a technical standpoint.

Referring to F i 5, since the main airfoil A and the ul ey 6 have the same axis, they will both e referred to as the pulley A6. From this figure of the drawing it will be observed that A-6 representing the main airfoil and pulley 6 are located at one end of the lever C which carries at its outer end the auxiliary airfoil B and pulley 4. Each pulley 6 and 4 is free to move on its center and also lever C may move about the center of airfoil A. The non-slipping belt is placed around'pulley 6 and 4 as previously described, and it will also be remembered that the pulley 6 associated with the main airfoil A has twice the diameter of pulley 4 associated with auxiliary airfoil B. The sections of the belt indicated as de and f-g are tan ent lines to both pulding to geometry the radii O-d, O'-e, O-f, and 0 g are perpendicular to the lines d-e, and f-g respectively. Therefore the lengths d-e and f-g cannot be changed. Su pose for example pulley 6 is caused to be stationary on its center and the lever C is moved u through an arc of 15 about the pivot Lines fg and de are at a constant angle to lever C. Therefore, when lever C is moved through 15 these two lines also move through 15. N 0w by the same rule radii 0-11 'and O-f move throu h 15 because they are always perpendicu ar to tangent line at point of tangency. Since pulley 6 is held stationary, the length of belt equal to the are 03-11 is removed, from the tan ent line below, and likewise arc ff is a ded to the tangent line above, but being that the length of these lines are constant, and equal, it means that a length of belt equal to are f-f' or d-d must run over the pulley 4 when the lever C is moved up through 15. The angle through which the airfoil B and pulley 4 rotates depends upon the ratioof its diameter to the diameter of fixed pulley A. In this case when lever C is moved ghrough 15f, airfoil B must rotate through If pulleys 4 and 6 were of the same diamstar, airfoil B would always remain parallel 13o to the same line throughout the range of the movemeut of lever C for any single position of the stationary pulley. The construction would not function properly if the pulleys were of the same diameter because a change in angle'of downwash giving airfoil B a positive lift, would have the same effect at all positions of the lever arm C and hence it would merely rise up until it was stopped by structural interference and stay there.

However, with the pulley eter of pulley 6 the auxiliary airfoil reaches its linnt of effectiveness or maximum lift with op osite inclinations at the same time airfoil does, assuming the burble point to be around 16. The auxiliary airfoil B will always move through the same angle as airfoil A, in reference to the body of the airplane, (see Fig. 6). As the downwash angle of airstream varies for any reason, the airfoil B is placed at an incidence to the airstream causing it, with lever C to be deflected either up. or down as the case may be but due to the planetary motion of airfoil B, caused by its flexible connection with the now fixed pulley G, it turns counter to lever arm C until it is again neutral or stable to the downwash airstream.

The downwash angle is the angle through which the airstream is deflected by any lifting surface of an airplane. The angle of downwash from the main planes is approximately one half the angle of incidence of the main planes measured from angle of no lift.

By way of illustrating an example, reference may be made to Fig. 7 of the drawings and the following table. This table would vary for different wing shapes, as the wings may be set at a different angle and also the neutral lift line may be different.

Angle of wing towindindegrees.. 0 a 4 6 s 10 12 14 Angleoibodyaxis to wind 4 -2 0 2 4 6 8 10 Angle of downwash relative to body axis -5 4 -3 -2 -1 0 1 2 horizontal flight position.

The downwash angle is an index, of the flying condition and attitude of the airplane.

This variation of the airstream furnishes the corrective force, which moves the aux iliary airfoil and by its fixed lever connection rotates the balanced stabilizing airfoil A.

Now suppose we have an air lane whose wings have a fixed setting of our degrees and a neutral lift line at 2 degrees the same as indicated in Figure 7. We are flying horizontally. The control lever is so set that both A and B airfoils are neutral or stable to the downwash airstream or are inclined at three degrees to body axis of plane. Now if the plane byreason of the rough air is precipitated into a position so that the wings are at an angle of 10 degrees to the wind, a change will take place in the 4: half the diam downwash from 3 degrees to 0 degrees which places airfoil A and auxiliary airfoil B at an incidence of 3 degrees to downwash airstream. Airfoil B, responds to this lift therefore the lever arni G now moves up 3 degrees placing airfoil A at 3 degrees additional incidence to airstream, and airfoil B turns down 6 degrees relative to arm C plac ing it neutral to the downwash airstream. The resulting lift of the 6 degrees incidence of airfoil A will raise the tail of plane back to normal at the same time the downwash angle returns to normal, causin the lever arm C to resume its original position. The

device will operate in similar manner when the tail is inclined upward the airplane.

Assuming fixed so it does not rotate, this change of incident angle will impress a righting moment on tail of airplane and tend to bringit back to normal. This tendency is known as static from the nose of that the stabilizing planeA is stability and is the method by which airplanes usually are stabilized. These righting moments will however set up oscillations caused by the over running of the righting moment and by the constant shifting of the center of pressure of the wings. An. airplane will be dynamically stable only if these oscillations diminish with time and ultimately die out.

The righting moment impressed upon the tail by the automatic adjustment of airfoil A will be twice as great as it would be if airfoil A was fixed in reference to body axis.

(Referrin to case above where A is 6 degrees inci ence instead of 3 degrees).

This ratio is dependent upon the relative sizes of the two pulleys. Owing tothe fact that the total control surface from which lon itudinal stability is derived, adjusts'its sel to oppose any oscillatory movements and, that the moment of inertia of airfoil A with its attached lever and airfoil B, about its axis, is so small compared to the forces acting upon airfoil B, that it will have no tendency to overrun, makin great dynamic stability possible by quick y damping out oscillations of tail.

The question of stability is closely connected to controllability. An airplane possessing a large amount of inherent stability is sometimes difficult to control, or in the words of the pilot, is said to be heavy on the controls. The automatic stabilizer however will give great inherent stability but being the movements of the main stabilizing plane is controlled by indirect means, its manipulation will be easy.

Therefore lever 12 is to select the angular setting of lever arm C at which airfoil B is neutral or stable to the downwash airstream, serving the same urpose as the conventional elevator contro The automatic feature of i the actual function of control r attitude desired. If

back, horizontal flight will still possible to fly at any the power is reduced for any reason, such as motor failure in multimotored plane, by setting lever 12 be possible the device makes it at a reduced speed.

This will not require the constant attention of the pilot as is usually the case with ordinary elevator control. The attitude can be held so that the wings will assume an angle very near the burble point giving maximum lift and minimum speed which will reduce the hazards and required skill in both taking off or landing.

One of the principal causes of serious accidents with airplanes is the stall, which is the condition of an airplane when from any cause it has lost the air speed necessary for support or control. This device eliminates the stall by turning the nose of the plane down for independently increasing the air speed when it is approaching the stalled condition, thus avoiding the nose dive caused by the wings losing lift due to the fact that the ang. of attack is beyond the burble point. This device can be so arranged that it would be impossible to place plane in a stalled condition voluntarily. In cases where air conditions are severely turbulent the device will always operate in a wa to ive control and horizontal or gliding flight 1n an upright position.

Without further description it is thought that the features and advantages of the invention will be readily apparent to those skilled in the art, and it will of course be understood that changes in the form, proportion and minor details of construction may be resorted to, without departing from the spirit of the invention and scope of the ap nded claims.

claim 1. In an air lane, the combination with a main wing of automatic stabilizing means comprising a main airfoil pivotally mounted at the tail of the fuselage, a centrally dis osed arm projecting from the forward an of the said main airfoil, an auxiliary airfoil havin said arm and located in the path of the downwash from said wing, a double pulley member loosely j ournaled coaxialiy with the pivot of the main airfoil, a flexible connection between said pulle and the pivotally mounted auxiliary airfoll, a manually shiftable lever, and flexible means controlled by said lever and passing over another portion of said double pulley.

2. In an airplane the combination with a main front wing of the airplane, of a rear ivoted airfoil, an arm carried b said airoil and projecting upwardly and forwardly from the axis of said airfoil, a controlling airfoil pivotally mounted at the front end of said arm and adapted to have a differential EILET MARTIN TORKELSON.

its medial portion pivoted in 

